Re: [PATCH v3 2/2] mmc: sdhci-of-dwcmshc: Add HPE GSC eMMC support

[Shawn Lin]

在 2026/03/13 星期五 3:25, Hawkins, Nick 写道:
> Hi Shawn, thank you for your input.
>
> See below:
>
> > -----Original Message-----
> > From: Shawn Lin <shawn.lin@xxxxxxxxx>
> > Sent: Thursday, March 12, 2026 3:25 AM
> > To: Hawkins, Nick <nick.hawkins@xxxxxxx>; ulf.hansson@xxxxxxxxxx; adrian.hunter@xxxxxxxxx; jszhang@xxxxxxxxxx
> > Cc: shawn.lin@xxxxxxxxx; robh@xxxxxxxxxx; krzk+dt@xxxxxxxxxx; conor+dt@xxxxxxxxxx; shawn.lin@xxxxxxxxxxxxxx; linux-mmc@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> > Subject: Re: [PATCH v3 2/2] mmc: sdhci-of-dwcmshc: Add HPE GSC eMMC support
>
>
> > > +static int dwcmshc_hpe_gsc_init(struct device *dev, struct sdhci_host *host,
> > > +				struct dwcmshc_priv *dwc_priv)
> > > +{
> > > +	struct regmap *soc_ctrl;
> > > +	int ret;
> > > +
> > > +	/* Disable cmd conflict check and configure auto-tuning */
> > > +	dwcmshc_hpe_vendor_specific(host);
> > > +
> > > +	/* Look up the GXP sysreg syscon for MSHCCS access */
> > > +	soc_ctrl = syscon_regmap_lookup_by_phandle(dev->of_node, "hpe,gxp-sysreg");
> > > +	if (IS_ERR(soc_ctrl)) {
> > > +		dev_err(dev, "failed to get hpe,gxp-sysreg syscon\n");
> > > +		return PTR_ERR(soc_ctrl);
> > > +	}
> > > +
> > > +	/* Set SCGSyncDis (bit 18) to disable sync on HS200 RX delay lines */
> > > +	ret = regmap_update_bits(soc_ctrl, HPE_GSC_MSHCCS_OFFSET,
> > > +				HPE_GSC_MSHCCS_SCGSYNCDIS,
> > > +				HPE_GSC_MSHCCS_SCGSYNCDIS);
> > > +	if (ret) {
> > > +		dev_err(dev, "failed to set SCGSyncDis in MSHCCS\n");
> > > +		return ret;
> > > +	}
> > > +
> > > +	sdhci_enable_v4_mode(host);
>
> > Sorry, I overlooked this part when in v2. But we enable it in
> > dwcmshc_probe() based on the capabilities, isn't it? Unless your
> > hardware didn't set SDHCI_CAN_64BIT_V4 but actually it does support
> > it? Then it perhaps should be a quirk, although we in general would like
> > to avoid more quirks... It depends on Adrian.
>
> > Btw, unlated to your patch, but th1520 did it the same way... Hmm
>
> The GSC's IP is configured with a 32-bit DMA AXI
> interface, so SDHCI_CAN_64BIT_V4 (caps bit 27) is not set by the
> hardware. However, the controller still requires Host V4 mode
> (HOST_CTRL2_R bit 12) to be enabled. Since dwcmshc_probe()
> only calls sdhci_enable_v4_mode() when SDHCI_CAN_64BIT_V4
> is set, the explicit call in dwcmshc_hpe_gsc_init() is necessary.

Okay, this aligns with previous assumption. So, we should either handle 
it via a quirk in the probe function and remove the call here, or simply 
add a comment to explain the context. This depends on Adrian's 
preference. I have no further questions. Thanks

> Thanks,
>
> -Nick H
>
>
>